Process Overview

An industrial laser beam under CNC/robotic control is focused onto a work piece, producing a melt pool into which a small amount of powder metal is injected, building up the part in a thin layer. The beam is moved to the next location based on CAD geometry, tracing out the part layer by layer. Some features of DMD systems are; a) patented closed-loop feedback control for the process that reduces heat input, b) patented coaxial nozzle with local shielding of melt pool allows consistent powder delivery and processing under open atmosphere, c) 6-axis DMDCAM software for additive manufacturing, d) 5-axis moving optics for heavy parts, and e) multi-material delivery capability.

Application

DM3D Technology (formerly POM Group) has developed a large proprietary material database for application in different environments. This includes components in automotive engines, tool & die industry, oil & gas industry, and many others. Some of the case studies are discussed below.

DMD applied cermet composite hardfacing:

DMD has been widely applied in the area of hardfacing to provide improved resistance against wear in oil & gas industry (Figure 1). This down hole tool was coated with cermet material containing 60% WC in a Ni-alloy matrix. With its multi-material delivery capability, DMD can apply graded coatings on such tools ranging from 10%WC coating on the part surface to 60%WC coating on the outermost surface. The extended tool life adds significant cost savings. Besides savings in tool costs and inventory reduction, reduction in down time due to less frequent tool changing, affects a significant saving through increased productivity.

Figure 1. (a) DMD hardfacing of a Oil drilling tool with cermet in DMD505, and (b) microstructure of the hardfacing material showing WC (60%) particles in a Ni-alloy matrix.

Heat checking/wear coating:

DMD is a value added technology that has been successfully applied in forging/stamping tools with great advantages. Figure 2 shows such an example where a forging die for the connecting rod has been coated using DMD process. To overcome the heat checking and wear damages during forging, the tool was built using low cost steel and a high temperature Co-based alloy was applied in the heat checking areas. In contrast to the mechanical bonding of the CVD/PVD/thermal spray coatings, DMD material is metallurgically bonded to the base steel and can withstand the thermal and fatigue loading of the forging process without chipping of the coating material. DMD built hardfacing material was about 6mm thick to sustain severe forging pressure and also allow for remachining of the tool multiple times. DMD applied tools had 4 times longer life over conventional tooling and resulted in significant cost savings, while reducing downtime.

Bi-Met Tooling:

Figure 3 shows the picture of an injection molding tool used for making seat belt clamps for cars. The tool has been manufactured using DM3D Technology’s proprietary Bi-Met tooling technology where tool steel is cladded on a copper base using the DMD process. High thermal conductivity of the copper base (6.0 times than that of steels) allows faster heat transfer leading to a significant reduction in cycle time (40%) while the steel clad on the molding surface provides the required strength and wear resistance of the tool.

Conclusions

DMD technology offers fully dense metallurgically bonded protective coatings on the parts with complex geometries. Its ability to deliver multiple materials allows it to create graded cermet coatings and/or application of different metals in different places. Application of the technology can affect significant cost savings through improving performance and productivity.